You've found Radio Kiss, an easy way to use a browser to play music from your JRiver library. It currently displays any playlists you have set for the Car Radio feature.
To add Car Radio playlists, start anything playing, then press and hold a button on the Playing Now page. You can name it, and tell JRiver whether to play exactly the current playlist or to use Play Doctor to vary it each time you play. The button will be saved with the name you chose and it will appear in Radio Kiss.
Right Click on the Car Radio buttons to auto-fill any unfilled buttons.
If you can't connect, check your firewall to make sure that ports 52100 to 52199 are opened. The wiki has a topic on Network Access.
Your browser must be new enough to provide support for HTML5. Try a different browser if necessary.
MC23 must be installed and MC or Media Server must be running.
You can test from the same machine by typing this in your browser: http://localhost:52199 (this starts Panel, then choose Radio).